more difficult to conceive of monads in space than of atoms; a point of indivisible activity might be at a certain point of space and a collection of the points of activity would constitute the mass which we call a body. Now, even if we grant that these points of activity are separated by space, yet when they were taken together they might produce upon the senses the impression of continuous space. Even in the case of what is called a body, say a marble table, every one knows that there are forces, that is to say, vacuums, between the parts. Since these vacuums, however, escape our sense organs, the body appears to us to be continuous, like the circle described by a moving succession of luminous points. In fact the bodies would be composed, as the Pythagoreans have already said, of two elements; the intervals (διαστήματα) and the monads (μόναδες); except that the Pythagorean monads were mere geometric points, while for Leibniz they are active points, radiating centers of activity, energies.
Regarding the difficulty of admitting into space forces non-extended and consequently having no relation to space, I grant that it is very serious. It cannot be raised, however, by those who consider the soul as a non-extended force and as an individual substance; for they are obliged to recognize that it is in space although in its essence it has no relation to space; there is, therefore, for them no contradiction in holding that a simple force is in space. If, on the other hand, it be denied that the soul is in space, that it is in the body, and even that it is in a certain part of the body, is it not clear that this would be attributing to the soul a character which is true only of God? To be sure, those who consider the soul as a divine idea, an eternal form temporarily united to an individual, might speak thus. Thus regarded, with the idealists or with Spinoza, the soul is not in space. But if the soul is represented as an individual and created substance, how can it be thought of except as in space and in the body to which it is united? Still more, therefore, in the case of monads will we be obliged to admit that they may be in space and then, as we have seen, the appearance of extension is explained without difficulty.
If, now, instead of admitting the reality of space we hold with Leibniz or with Kant that it is ideal, the system of monads offers no longer any serious difficulty, except from the point of view of those who deny the plurality of individual
